I know to preserve darker clothes, you add vinegar to the initial wash. Can this be done during the 2nd wash?

I think it actually works better to use it in the final rinse, as it acts as a softener plus removes soap residueI know to preserve darker clothes, you add vinegar to the initial wash. Can this be done during the 2nd wash?
Sure, I also turn my darker clothes inside out and wash on the cold/cold wash cycle with Woolite and I hang them to dry... Good luck